Cart
0
Not to be the bearer of bad news (again), but household energy bills are undoubtedly rising again and with the UK legally committed to reaching net-zero greenhouse gas emissions by 2050, ‘retrofit’ has become one of the government’s preferred answers to Britain’s energy problems. The UK government defines retrofit as “introduction of new materials, products and technologies into an existing building to reduce the energy needed to occupy that building”. As most houses in the UK were built well before the modern standards of energy efficiency were established, many houses struggle to efficiently contain heat.
The principle is sensible, involving the introduction of new materials and technologies into an existing building to reduce the energy required to occupy it. This can mean insulating a loft, filling cavity walls with polystyrene (EPS) Beads or installing solar panels and heat pumps.
In addition to financial savings, retrofitting provides social and environmental benefits. The reduction in the amount of energy needed to heat homes, leads to the reduction in carbon dioxide emissions and contribute to the UK’s Net Zero goal. This reduction in energy demand also reduces reliance on fossil fuels and helps improve air quality. Furthermore, better-insulated houses correlate with improved health, as they reduce damp and mould that can contribute to respiratory illness.
Photo: UK Parliament, licensed under CC BY 3.0.
Andy Burnham became Prime Minister of the United Kingdom on 20 July 2026 and has promised ‘the biggest council house building-programme since the post-war period’, suggesting a sharp rise in construction rates compared to recent years.
With Over 1.3 million households trapped on local waiting lists, it is evident that Britain undoubtedly needs to improve its housing stock. Homes and ‘other’ buildings account for about 1/5 of UK greenhouse gas emissions. Although undeniably the average energy-efficiency of a UK home has increased from 45 points in 1996 to 68 in 2024; 44 percent of homes still are below energy-efficiency bands A-C. Privately owned and rented homes remain notably less efficient than social housing.
General political discussion often treats retrofit as though every improvement is worthwhile to the average homeowner and automatically a sound investment. In my opinion, I’m afraid it is not.
Britain is desperately calling for a retrofit strategy that is based on payback periods, building condition and household circumstances: not just a ‘virtue-signalling’ broad list of technologies carrying a green label.
The urgency is clear for UK household’s as from July to September 2026, Ofgem’s energy price cap for a typical dual-fuel household paying by direct debit is £1,862 a year, 13% higher than the previous quarter. Gas under the cap costs an average of 7.33p per kilowatt-hour, while electricity costs 26.11p.
If you were to consider loft insulation, the energy saving trust estimates that professionally installing 270mm of insulation in an uninsulated semi-detached loft costs approximately £900. Topping up existing insulation from 120mm to 270mm costs roughly £750 and will cost a lot less when completed as a DIY project.
Loft insulation using mineral wool (Earthwool) and rigid PIR insulation boards such as Celotex.
The economics become seriously less convincing as the work becomes more ambitious. Average retrofit costs for a semi-detached house include approximately £1,700 for floor insulation, £12,000 to £18,000 for solid-wall insulation, £11,000 for an air-source heat pump and £12,000 for A-rated double glazing.
Double glazing illustrates how retrofitting can become seriously less convincing well. For a homeowner, replacing all previously installed single glazing with A-rated double glazing is estimated to save around £140 a year, compared to the average installation cost equating to £12,000, the payback period could exceed 80 years. This is before maintenance, finance costs and energy price changes are considered.
This is where the concept of diminishing returns matters.
Essentially a poorly insulated home resembles a kind of leaking bucket. And plugging the largest holes is most of the time inexpensive. For example, an easy plug such as draught proofing a door may generate noticeable benefits at a low cost. The common mistake is to assume that because the first £1,000 spent on a property produces a strong return, the next £10,000 will do the same.
If a homeowner were to be sensible, and therefore follow my advice, a retrofit programme should begin with thorough diagnosis and not expensive installation. This should include reviewing their EPC, inspect the property for damp or maintenance problems and identify where heat is being lost. Logical sustainable advancements such as draught-proofing, loft insulation and heating controls should usually come before costly technologies such as heat pumps or external wall insulation.
The financial case should be tested using a simple payback calculation: Installation cost divided by estimated annual savings. A £900 measure saving £200 a year pays for itself in around four and a half years while a £12,000 upgrade saving £140 annually could take more than 80 years.
There is no doubt in my mind that Retrofit is necessary, but government policy has and will often treat every expensive green upgrade as automatically worthwhile in my opinion, it is pathetic that homeowners are pressured into costly technologies with immensely weak payback periods simply to satisfy political targets
